1. Field of the Invention
The present invention relates to a tensioning device for tensioning a plastic band.
2. Discussion of the Background
Tensioning devices for strapping machines are intended to tension a plastic band, which is guided around an article to be strapped and is tightened against it to a predetermined tensile stress so that the band bears snugly against the article to be strapped. Strapping machines currently produced have a tensioning device with a tensioning element which is designed in the manner of a roller. This tensioning element is arranged on a shaft connected to a driving motor, and is designed to have a flattened portion in one sector on its circumference. That edge of the flattened portion which is at the rear in the direction in which the tensioning element is rotated to tension the plastic band forms a gripping location for the plastic band. A convex gripping surface of a clamping element interacts with this gripping location to hold the plastic band. The clamping element is mounted eccentrically on the tensioning element with respect to the axis thereof With increasing tensioning force the clamping action on the plastic band between the gripping surface and the flattened gripping location increases. If very high tensioning forces are required, this can lead to the plastic band being damaged.